Contact lenses have been described as being useful in correcting presbyopia. Some methods and devices for treating presbyopia or improving vision of presbyopic subjects have been described, such as in EP0201231A1, EP2183639A1, GB2086605A, U.S. Pat. Nos. 5,220,359, 5,715,031, 5,754,270, 5,771,088, 5,835,192, 6,322,213, 6,520,638, 6,540,353, 7,517,084, 7,625,086, and 7,753,521, US20090051870A1, US20100321632A1, US2011310347A1, WO0008516, and WO0135880.
As one example, in a monovision correction system, a presbyopic person wears one contact lens having a design for only correcting distance vision in one eye (e.g., the lens has a single labeled sphere power to correct distance vision), and a second contact lens having a design for only correcting near vision in the other eye (e.g., the lens has a single labeled sphere power to correct near vision). Monovision correction seems to provide better results for presbyopic subjects requiring low Add power correction (e.g., low Add patients). Higher Add subjects tend to experience more visual discomfort or visual compromise with monovision systems, such as blurred images and the like.
As another example, multifocal contact lenses having aspheric optics to provide a relatively smooth transition in optical power across the lens, or multifocal contact lenses with distinct optical zones that alternate between distance and near refractive powers have also been described as being useful for correcting presbyopia. Examples of contact lenses for correcting presbyopia include: the ACUVUE OASYS for Presbyopia (Vistakon, Jacksonville, Fla., USA; lens pairs consisting of two center-distance lenses); the PUREVISION MULTIFOCAL (Bausch & Lomb, Rochester, N.Y., USA; lens pairs consisting of two center-near front surface aspheric lenses); the AIR OPTIX AQUA MULTIFOCAL (Ciba Vision, Duluth, Ga., USA; lens pairs consisting of two center-near aspheric lenses); and FREQUENCY 55 MULTIFOCALS, PROCLEAR MULTIFOCALS, and BIOFINITY MULTIFOCALS (each from CooperVision, Pleasanton, Calif., USA; lens pairs consisting of a center-distance lens and a center-near lens).
Although multifocal contact lenses provide vision improvement to many presbyopic subjects, multifocal contact lenses can produce secondary images or “ghost” images, as perceived by the subject. This ghosting is likely to be attributed to defined zones and/or narrow transitions between distance and near powers of the multifocal contact lenses. It remains a challenge to provide both clear distance visual acuity and clear near visual acuity to the subject, let alone do so and reduce or avoid visual discomfort or visual compromise, such as ghosting, contrast loss, and the like. This challenge is especially true for subjects requiring medium or high Add powers in contact lenses (such as subjects requiring an Add power correction greater than +1.00 diopter).
To address this challenge and meet the requirements of eye care practitioners (ECPs) and presbyopic subjects, contact lens manufacturers currently offer multiple lens choices for an ECP to select from and prescribe. Although the relatively large number of options available to the ECP and subject or patient appears beneficial, the large number of options can reduce the efficiency of the ECP by requiring more time to find the desired lens combination for a particular subject from among the large number of options. Providing large number of lens combinations to ECPs is also undesirable for a contact lens manufacturer, or distributor, or both because the increased number of lens designs and combinations for different sphere powers and Add powers result in increased inventory that must be made and stored to provide to the ECP or the subject.
Based on the increasing number of presbyopic people, there continues to be a need for new multifocal contact lenses which provide effective vision correction to presbyopic people.